DD is in her second year of primary. All of the older students moved up to lower el or changed to public school this year. There are older kids (in age) in her class, but they are also second year M students. I'm feeling like DD may be getting cheated on the "learn from the older students" concept. Is there anything that I should address with her teacher? Not sure what she can do about the situation, short of a M family moving to the school.

There is little school can do, short of aggressive marketing and PR too get/keep third year-kindergarten students. Sometimes it is just the way the cookie crumbles, and in these economic times, a lot of kids are going on to public K instead of staying for their 3rd year in Primary.

That being said, the teacher and the school can d things to compensate. They can make sure the kids have more exposure to the kids in Elementary. Shared lunch time, classroom helpers, a joint reading time are just some examples. A combined recess for Primary and Lower El. sometimes works wonders.